Abu Musa says that once I said to Hazrat Aisha (may Allah be pleased with her), "I want to ask you a question but I feel shy." She replied, "Do not be shy, ask, I am your mother." So he asked about the man who "overcomes" his wife but does not ejaculate. She replied that the Prophet (peace and blessings be upon him) said, "When the private part meets the private part, ghusl becomes obligatory."